Additional studies of the mechanisms by which "Fenton" oxidation (i.e., oxidation effected by reactive intermediates formed in mixtures of hydrogen peroxide with ferrous ion) occurs have been conducted. Further evidence against a kinetically significant role for hydroxyl radical was obtained. The reactivity of the reactive iron-oxo intermediates with other organic substrates, including amino acids and nucleic acid constituents, was characterized. In addition, a series of unusual N- nitroso compounds formed by reacting various nucleophiles with nitric oxide is being investigated.